<div class="interval-input-element">
  <input class="form-control"
        ng-model="vm.quantity"
        ng-change="vm.updateSeconds()"></input>
  <select class="form-control"
          ng-options="period.label for period in vm.periods"
          ng-model="vm.selectedPeriod"
          ng-change="vm.updateSeconds()"></select>
</div>